Trying to get caught up on my posts since Oshkosh. Its been a busy and productive week in the ol' aircraft factory. Some pretty cool progress has been made and its been exciting, check it out. I got the main wing skeletons hanging in my mobile wing stand and leveled them up.
I wanted to test a theory I had about wing twist. The plans say to remove twist from the skeleton once you get it hanging. My argument is that if these are pre-punched and this is not a 'jig' but in fact just a stand to make it easier to work on the wings, why do we need to worry about wing twist? I have heard of people building these wings without a stand, on a work bench. Surely they are not checking for 'twist' while doing that.
Consider this scenario, if I mount the wing skeletons, check for wing twist and actually find there is twist...adjust it out and then when I install the skins and they dont match, what do I do then? You see where I am going with this? The pre-punched holes WILL create straight wings without twist by default, and if not you got big problems...computers dont lie, those holes are located by a computer. Now keep in mind you will get twist if one of your mounting brackets is not level while the other one is, but I contend even then it will straighten out when you install the skins...it has to. The skins will bring the skeleton into shape.
So to test the theory, I used only the top mounting angles and left the bottom ones off and ignored the possiblity of twist. As I said, I leveled the main angle brackets with a bubble level and also took the sag out of the middle so I had a nice straight spar. I then cleco-ed the skins in place. Not only did the holes match up amazingly well, but when I was done I checked for twist...not an ounce, it was 'dead on' as I suspected it would be. This is a well engineered kit.
My conclusion is that the lower mounting brackets and the twist check are not needed. As a builder, its up to you to do what you feel is appropriate but I feel very comfortable with this strategy. My opinion, and take it for what its worth, is too many things in the construction of these kits is done without question because thats what everybody does. Sometimes it just adds up to a whole bunch of unneccessary work. As an Engineer, I am trained to ask 'why'...the concept of match drilling will be next rant, but that will be another post! :) Enjoy the pics.
My right and left wing mirrored on my mobile wing stand. The concept works pretty good, although I probably will be done with the wings before the snow gets too bad so I could see me not even utilizing the 'mobile' option, but its there if I need it.
Here is my strategy for taking the sag out of the wing. A piece of all-thread going through a 2x6, worked slick and is also mobile with the stand.
Here's a shot of the 'wing walk' area. Extra ribs and a 'doubler' beef this up so people can walk on the wing entering and exiting the aircraft...I always wondered how they did this, now I know!
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